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ELECTRICAL SCIENCE > BASIC AC > Flashcards

BASIC AC Flashcards

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1
Q

More than ______ of electric energy is generated by AC machines

A

90%

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2
Q

AC generation can be accomplished economically in _____ power plants that may be located where fuel and water are abundant

A

LARGE

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3
Q

Types of industry that a great portion of the AC energy is converted to DC

A
  1. Railway Transportation
  2. Communication System
  3. Home
  4. Electrochemical Industry
  5. Motor Applications
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4
Q

AC/DC Power Supply

A

AC Supply -> Transformer -> Rectifier -> Smoothing (Filter/Capacitor) -> Regulator -> Load

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5
Q

Why is AC generation more ideal than DC generation?

A

Because DC can’t be stepped down or stepped up. In order to step up or down a DC, we need to convert it first to AC which is feasible but expensive.

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6
Q

In DC systems, energy must be transmitted from generator to consumer at essentially the same EMF as it is generated; this is usually restricted to such low values as _____, ______, and ______.

A

250V, 600V, 1500V

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7
Q

Two effects of having lower current thru the transmission line due to stepping up of voltage via transformer

A
  1. Lower line losses (I²R) over long distances (reduce copper loss)
  2. Lesser diameter transmission wires needed (save copper)
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8
Q

T or F. Transformer has no moving parts.

A

TRUE

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9
Q

In GMEC, 18kV is stepped up to _______

A

230kV

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10
Q

AC generator is also referred to as ______

A

ALTERNATOR

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11
Q

When the wire loop or coil rotates one complete revolution, or 360°, _______ is produced

A

ONE FULL WAVEFORM

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12
Q

It is the time interval between two occurrences of the wave

A

PERIOD (T)

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13
Q

It is the number of oscillations (cycles) that take place in a given amount of time

A

FREQUENCY (f)

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14
Q

It is the angular displacement of any element of the wave per unit of time or the rate of change of the phase of the waveform

A

ANGULAR FREQUENCY (ω)

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15
Q

T or F. Electrical angle is a degree.

A

FALSE.

RADIAN

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16
Q

π rad is equal to _____

A

180°

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17
Q

Average voltage in a complete/full sine wave or one full cycle

A

ALWAYS ZERO

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18
Q

It is the area under the curve within a given time period

A

AVERAGE VALUE

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19
Q

It is the square root of the average (mean) of the square of the alternating amplitude values

A

EFFECTIVE/RMS VALUE

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20
Q

It is defined as the AC value that will give the same heating effect as an equivalent DC voltage

A

EFFECTIVE/RMS VOLTAGE

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21
Q

The measure of the extent that a graph of the sinusoidal function is moved horizontally to the left or to the right

A

PHASE SHIFT (φ)

22
Q

φ can be determined by measuring the shift of the _________ of the wave.

A

POSITIVE SLOPE ZERO CROSSING

23
Q

Sinusoid is shifted to the left when phase shift is positive

A

SINUSOIDS LEADS THE REFERENCE

24
Q

Sinusoid is shifted to the right when phase shift is negative

A

SINUSOIDS LAGS THE REFERENCE

25
Q

T or F. The slower the rotor rotates, the more cycle per second of voltage is induced

A

FALSE

FASTER (speed of rotation ∝ frequency)

26
Q

T or F. Frequency is also directly proportional to the number of main field poles

A

TRUE

27
Q

Electrical degrees relate to _______ of the sinusoid

A

ELECTRICAL FREQUENCY

28
Q

Mechanical degrees relate to ______

A

MECHANICAL ROTATION

29
Q

T or F. In a 2-pole alternator, one electrical cycle is formed in one mechanical revolution

A

TRUE

30
Q

In a _____ alternator, two electrical cycles are formed in one mechanical revolution

A

4-POLE

31
Q

The governing principles on the relationship between electrical frequency and speed rotation for single phase alternators apply to ________ alternators.

A

3-PHASE

32
Q

Scalar quantities are numbers that have ______

A

MAGNITUDE BUT NO DIRECTION

33
Q

Vector quantities indicate ______

A

MAGTINUDE AS WELL AS DIRECTION

34
Q

The association that recommended the term phasor instead of vector to be applied to lines that are given direction wrt a reference when they are used to replaced sinusoidal functions

A

AMERICAN STANDARDS ASSOCIATIONS (ASA)

35
Q

T or F. A phasor is a vector.

A

FALSE

NOT

36
Q

I = 200∠60° Amps

A

POLAR FORM

37
Q

I = 100 + j173.21 Amps

A

RECTANGULAR FORM

38
Q

A _____ may be specified by the magnitude of its projection on the x and y axes

A

PHASOR

39
Q

Methods to derive the resultant of phasors

A

TIP-TO-TAIL METHOD
COMPONENT-BREAKDOWN METHOD

40
Q

T or F. In a transformer, the voltage frequency at the primary side is not always the same as the voltage frequency at the secondary side

A

FALSE

ALWAYS

41
Q

T or F. Np < Ns - step down transformer

A

FALSE.

STEP UP

42
Q

Ip > Is

A

STEP UP TRANSFORMER

43
Q

Vp > Vs

A

STEP DOWN TRANSFORMER

44
Q

n>1

A

STEP DOWN

45
Q

n<1

A

STEP UP

46
Q

It steps up the 18kV plant-generated voltage to the transmission voltage of 230kV

A

GMEC GSUT (Generator Station Unit Transformer)

47
Q

It steps down the 18kV plant-generated voltage to the auxiliary load voltage of 6kV

A

GMEC UAT (Unit Auxiliary Transformer)

48
Q

It steps down the 230kV transmission line voltage to the auxiliary load voltage of 6kV

A

GMEC S/SAT (Start-up/Standby Auxiliary Transformer)

49
Q

During _____ or ______, GMEC S/SAT is used in case plant generator has no output

A

SHUTDOWN or INITIAL STARTUP

50
Q

What is the generator output voltage of GNPD?

A

26kV

51
Q

SDAT stands for ____

A

STEP DOWN AUTO TRASFORMER

ELECTRICAL SCIENCE (2 decks)

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